In a variety of applications, elongated webs or strips of material are provided with edge perforations which are used subsequently to drive or guide the strips through other apparatus. For example, photographic film strips for personal cameras have long been provided with a continuous row of evenly, closely spaced perforations along both edges of the strips, the perforations being used during spooling of the strips, during winding of the film through the camera and during processing of the exposed film strips. Similarly, numerous paper products are known in which continuous rows of evenly, closely spaced perforations are provided along the edges of the paper for use in feeding the paper through a processing apparatus such as a printer. Apparatus and methods for producing such continuous rows of evenly, closely spaced perforations are known, some requiring the use of sets of punches and dies which are actuated simultaneously as the strip is intermittently stopped for perforating; and some requiring the use of rotating drums with punches which perforate the continuously moving strip. The strip is then cut into shorter strips each having continuous patterns of perforations, such as strips for various numbers of exposures in the case of photographic film products.
Applications for photographic film strips and similar strip products have been developed in recent years for which the familiar continuous rows of evenly, closely spaced perforations are no longer needed, though other, even patterns of widely spaced perforations are still required to indicate position along the strip or to indicate the lead or tail end of the strip and the like. See, for example, commonly assigned U.S. Pat. No. 4,860,037. Because the perforations are widely spaced and groups of perforations are separated by leader/trailer sections having no or few perforations, known apparatus of the type previously mentioned are not suitable. In the known intermittently actuated equipment, difficulties are encountered in moving the strips at the higher operating speeds desired for efficient production and undesirably complex and expensive modifications are needed to provide the capability of selectively producing an alternative, widely spaced pattern of perforations separated by leader/trailer sections. In the known rotary equipment, more than adequate operating speeds can be obtained, but mechanisms for selectively inhibiting the punches on the rotating drums are extremely complex and expensive.
Thus a need has arisen for apparatus and methods for perforating a strip of film or other web at high speed and with patterns widely spaced of perforations separated by leader/trailer sections. Such an apparatus and method must have the capabilities of positioning such perforations with great accuracy along the strip, changing the numbers of pitches of such perforations for strips of different lengths and changing the distance skipped between patterns for strips of different lengths.